Fig. 5. (  A ) Bicoherence peak frequency (○) and bicoherence values (□) regarding α spindle ranges during the change of sevoflurane concentration. Higher sevoflurane concentration significantly shifted α peaks to lower frequencies (  P < 0.05). Bicoherence values in α peaks tended to decrease with sevoflurane increases from 1% to 3%, but no statistical significance. Significant differences: * between 1% and 2% sevoflurane; ** between 1% and 3% sevoflurane; # between 2% and 3% sevoflurane. (  B ) Bicoherence peak frequency (○) and bicoherence values (□) regarding δ-θ range during the change of sevoflurane concentration are summarized. Higher sevoflurane concentration significantly shifted δ-θ peaks to lower frequencies (  P < 0.05). Bicoherence values in δ-θ peaks increased with increased sevoflurane from 1% to 2% and 3% (  P < 0.05). Significant difference between: * 1% and 2% sevoflurane; ** 1% and 3% sevoflurane; # 2% and 3% sevoflurane.